Biomedical subjects

Małgorzata Lekka

Publications and source records attributed to Małgorzata Lekka.

6 recordsLinked to original sources

PubMed2006

Lectin-carbohydrate affinity measured using a quartz crystal microbalance.

The association of two molecules is described by two parameters, association equilibrium and association rate constants, which are characteristic for a given type of interaction. Usually, they are determined for interacting molecules dissolved in solution. However, for many applications one type of molecules is immobilized on a substrate, which may influence the binding kinetics. The studied complex of concanavalin A and carboxypeptidase Y belongs to the lectin-carbohydrate type of interaction involving the recognition of oligosaccharide moieties. The concanavalin A was immobilized on a gold electrode of quartz crystal, while carboxypeptidase Y was added to a buffer (Tris-buffered saline). The constants describing the association of the investigated molecules were determined on the basis of measurements performed using a quartz crystal microbalance in liquid. The obtained values were (0.59+/-0.01)x10(6) M(-1) for the association equilibrium constant and (5.6+/-0.1)x10(4) M(-1)s(-1) for the association rate constant. The saturation binding experiment gave another value of the association constant, (2.7+/-0.02)x10(6) M(-1). The comparison of obtained values with previously published ones verifies that the molecule orientation and binding site accessibility for specific ligands could influence the association equilibrium constant value. The presented measurements demonstrate the ability of a quartz crystal microbalance to detect and to evaluate the association process occurring between molecules.

Journal Article↗

PubMed2006

Stiffness of normal and pathological erythrocytes studied by means of atomic force microscopy.

During recent years, atomic force microscopy has become a powerful technique for studying the mechanical properties (such as stiffness, viscoelasticity, hardness and adhesion) of various biological materials. The unique combination of high-resolution imaging and operation in physiological environment made it useful in investigations of cell properties. In this work, the microscope was applied to measure the stiffness of human red blood cells (erythrocytes). Erythrocytes were attached to the poly-L-lysine-coated glass surface by fixation using 0.5% glutaraldehyde for 1 min. Different erythrocyte samples were studied: erythrocytes from patients with hemolytic anemias such as hereditary spherocytosis and glucose-6-phosphate-dehydrogenase deficiency patients with thalassemia, and patients with anisocytosis of various causes. The determined Young's modulus was compared with that obtained from measurements of erythrocytes from healthy subjects. The results showed that the Young's modulus of pathological erythrocytes was higher than in normal cells. Observed differences indicate possible changes in the organization of cell cytoskeleton associated with various diseases.

Cell Shape↗

PubMed2006

Specific detection of glycans on a plasma membrane of living cells with atomic force microscopy.

Among the many alterations of cancer cells is the expression of different surface oligosaccharides. In this work, oligosaccharide expression in living cells (cancer and reference ones) was studied with atomic force microscopy by using lectins as probes. The unbinding force obtained for the same lectin type (concanavalin A or Sambucus nigra) suggested slightly dissimilar structures of binding sites of the same ligand type. For the lectin from Phaseolus vulgaris, a much larger unbinding force indicated a distinct structure of the binding site in cancer cells. The unbinding probability confirmed a higher content of both sialic acid and mannose-containing ligands in cancer and reference cells, respectively. These results demonstrate the potential of atomic force microscopy to directly probe the presence of molecules on a living cell surface, together with the quantitative description of their expression.

Cell Line, Tumor↗

PubMed2006

Erythrocyte stiffness in diabetes mellitus studied with atomic force microscope.

The mechanical properties of erythrocyte membrane have been studied using an atomic force microscope. Measurements were carried out on blood samples taken from 7 diabetes mellitus patients and 8 healthy individuals. For each blood sample a distribution of a Young's modulus was constructed. It has been found that both the mean value and the width of the distribution in diabetic patients exceed the corresponding results for healthy persons by a factor greater than 3. The high sensitivity of the atomic force microscopy and the ability to measure the full distribution of the erythrocyte membrane Young's modulus makes it a unique, powerful and promising tool in studies of the membrane stiffness of red blood cells.

Diabetes Mellitus↗

PubMed2005

Friction force microscopy as an alternative method to probe molecular interactions.

Friction force microscopy was applied to study protein-carbohydrate interactions that are important in many cellular recognition processes. The expression and structure of carbohydrates can be investigated using lectins as molecular probes since they recognize different types of sugar molecules. Lectins (concanavalin A and lentil lectin, recognizing mannose-type carbohydrates) were attached to the probing tip and carboxypeptidase Y (possessing complementary carbohydrates) was immobilized on a modified glass surface using microcontact printing. The results obtained from friction force maps and dependencies on the loading rate (measured in a physiological buffer) were divided in two distinct groups. The first group of results obtained for lectin-protein complexes was assigned to molecular recognition events, whereas the other including all control measurements was attributed to nonspecific interaction. All results presented here indicate that friction force microscopy can be successfully employed to study recognition processes.

Journal Article↗

PubMed2005

Expression of prostate specific membrane antigen in androgen-independent prostate cancer cell line PC-3.

During the progression of prostate cancer from androgen-dependence or sensitivity to androgen-independence, the overall expression of prostate specific membrane antigen (PSMA) increases with its appearance in plasma membrane. However, surprisingly some androgen-independent metastatic prostate cancer cell lines do not express this protein. Estradiol (E2) and basic fibroblast growth factor (bFGF) due to their recognized and strong involvement in prostate growth, development, and pathology were selected with the aim of restoring the expression of PSMA in markedly dedifferentiated prostate cancer PC-3 cells and in Du 145. E2 (10(-7)-10(-11)M) and bFGF (10ng/ml) stimulated the expression of mRNAs for PSMA (2- to 4-fold increase) that apparently were further translated and processed to its membrane form in LNCaP, PC-3, and Du 145 cells. The values of interaction force between the same anti-PSMA antibodies and all studied cells were almost identical (45-64pN), indicating antigenic similarity of the membrane form of PSMA expressed in LNCaP, PC-3, and Du 145 cells.

Androgens↗